The broad aim of this project is to understand how the feline striate cortex is organized, and how the organization is laid down during development under the influence of neonatal experience. A mathematical model of cortical development, based on the synaptic competition hypothesis of Wiesel and Hubel, is being elaborated and tested by experiments on cats and kittens. Single unit recordings in normal adult cats are used to investigate the mechanisms of directional selectivity and orientation selectivity in striate cortex cells, and the detailed structure of orientation columns. Recordings from kittens are used to determine the effects of neonatal visual deprivation or cortical inhibitor mechanisms. Attempts will be made to stain striate cortex cells with Procion Yellow in order to identify morphologically the types of cells exhibiting various kinds of plasticity. Concentric double-barreled beveled pencil electrodes will be used for this purpose.